1. Field of the Invention
The present invention relates to a method of forming a patterned thin film by etching a film to be patterned, and to a method of manufacturing a thin-film magnetic head, the method including the step of forming a magnetic layer by etching a film to be patterned.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write (recording) head having an induction-type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a write head. To achieve this, it is required to implement a write head of a narrow track structure wherein the width of top and bottom poles sandwiching the write gap layer on a side of the medium facing surface (air bearing surface) is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
A write track width of 0.2 to 0.3 xcexcm has been recently required to implement a composite thin-film magnetic head that has an areal recording density of 40 to 60 gigabits per square inch.
In many of prior-art thin-film magnetic heads the magnetic layer that defines the write track width is made of NiFe and formed through plating. The saturation flux density of NiFe is increased by increasing the proportion of Fe. A well-known type of NiFe having a high saturation flux density is made up of 45 weight % of Ni and 55 weight % of Fe and exhibits a saturation flux density of about 1.6 T. If such a type of NiFe that has a high saturation flux density is utilized, the magnetic layer having a high saturation flux density is formed.
However, if the write track width is reduced as described above, it is impossible to obtain a sufficient magnetic flux in the air bearing surface even though the magnetic layer that defines the write track width is made of a type of NiFe that exhibits a high saturation flux density. As a result, it is likely that writing characteristics, such as an overwrite property that is a parameter indicating one of characteristics when data is written over existing data, are made insufficient.
To solve this problem, it is possible that the magnetic layer that defines the write track width is made of a high saturation flux density material, such as FeN or FeCo, that has a saturation flux density of about 2.0 T, for example, that is greater than the saturation flux density of NiFe. To form a patterned thin film made of such a high saturation flux density material, a method of etching a film to be patterned that is formed through sputtering is generally used. The etching method is ion milling, for example.
Reference is now made to FIG. 10A to FIG. 14A and FIG. 10B to FIG. 14B to describe an example of a method of manufacturing a thin-film magnetic head, the method including the step of forming the magnetic layer that defines the write track width by etching a film to be patterned through ion milling as described above. FIG. 10A to FIG. 14A are cross sections each orthogonal to the air bearing surface of the thin-film magnetic head. FIG. 10B to FIG. 14B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 10A and FIG. 10B, an insulating layer 102 made of alumina (Al2O3), for example, is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a read head.
Next, on the bottom shield layer 103, alumina, for example, is deposited through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reading is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a read head and a write head.
Next, as shown in FIG. 11A and FIG. 11B, on the bottom pole layer 108, a write gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.15 xcexcm is formed. Next, a portion of the write gap layer 109 is etched to form a contact hole 109A to make a magnetic path.
Next, a high saturation flux density material such as FeN or FeCo is sputtered over the entire surface to form a film to be patterned having a thickness of about 1.0 to 2.0 xcexcm. On this film to be patterned photoresist masks 112a and 112b made of patterned photoresist layers and having a thickness of about 5 xcexcm, for example, are formed. The photoresist mask 112a is formed on a portion of the film to be patterned that will be a pole portion. The photoresist mask 112b is formed on a portion of the film to be patterned located above the contact hole 109A.
Using the photoresist masks 112a and 112b as masks, the film to be patterned is etched through ion milling to form a pole portion layer 111a and a magnetic layer 111b. The pole portion layer 111a makes up the pole portion of the top pole layer. The magnetic layer 111b is connected to the bottom pole layer 108. The pole portion layer 111a has a width equal to the write track width.
Next, as shown in FIG. 12A and FIG. 12B, the photoresist masks 112a and 112b are removed. Next, a portion of the write gap layer 109 around the pole portion layer 111a is etched, using the pole portion layer 111a as a mask. Furthermore, the bottom pole layer 108 is etched by 0.3 xcexcm only, for example. As shown in FIG. 12B, the structure thereby obtained is called a trim structure wherein the sidewalls of the pole portion layer 111a, the write gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 113 made of an alumina film, for example, and having a thickness of 2 to 3 xcexcm is formed on the entire surface. The insulating layer 113 is then polished to the surfaces of the pole portion layer 111a and the magnetic layer 111b and flattened.
Next, on the flattened insulating layer 113, a first layer 114 of a thin-film coil made of copper (Cu), for example, and having a thickness of 1 to 2 xcexcm is formed for the induction-type write head. In FIG. 12A numeral 114a indicates a portion of the first layer 114 that will be connected to a second layer 116 of the coil described later. Next, a photoresist layer 115 having a specific shape is formed on the insulating layer 113 and the first layer 114. Heat treatment is performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 13A and FIG. 13B, on the photoresist layer 115, the second layer 116 of the thin-film coil having a thickness of 1 to 2 xcexcm is formed. Next, a photoresist layer 117 having a specific shape is formed on the photoresist layer 115 and the second layer 116. Heat treatment is performed at a specific temperature to flatten the surface of the photoresist layer 117.
Next, a yoke portion layer 118 made of a magnetic material and having a thickness of about 2 to 3 xcexcm is formed on the pole portion layer 111a, the photoresist layers 115 and 117, and the magnetic layer 111b. The yoke portion layer 118 makes up the yoke portion of the top pole layer.
Next, as shown in FIG. 14A and FIG. 14B, an overcoat layer 119 made of alumina, for example, and having a thickness of 20 to 40xcexcm is formed to cover the yoke portion layer 118. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface 130 of the thin-film magnetic head including the write head and the read head. The thin-film magnetic head is thus completed.
It is easy to achieve a small track width if the top pole layer that defines the write track width is made up of the pole portion layer 111a and the yoke portion layer 118, as shown in FIG. 14A and FIG. 14B, instead of forming the top pole layer made up of one layer. In addition, when the write track width is reduced, it is required that the pole portion layer 111a that defines the write track width is made of a high saturation flux density material such as FeN or FeCo, as described above. To form the pole portion layer 111a made of such a high saturation flux density material, the method generally used is to etch the film to be patterned that is formed through sputtering, as shown in FIG. 11A and FIG. 11B. The etching method is ion milling using the photoresist mask 112a as a mask.
However, the etching rate at which the film to be patterned made of a high saturation flux density material such as FeN or FeCo is etched through ion milling is very low, that is, about 30 to 40 nm per minute. Therefore, it takes a long time to form the pole portion layer 111a by etching the film to be patterned through ion milling. When etching is performed through ion milling, a poor pattern profile is obtained and the cross-sectional surface of the film patterned forms an angle of 50 to 70 degrees with respect to the bottom surface. It is therefore difficult to implement a small track width of 0.3 xcexcm or smaller. In addition, when etching is performed through ion milling, the angle formed between the cross-sectional surface and the bottom surface of the patterned film obtained becomes smaller as the thickness of the film to be patterned increases. It is therefore more difficult to implement a small track width.
In Published Unexamined Japanese Patent Application Heisei 6-44528 (1994), a technique is disclosed for processing a magnetic substance layer by reactive ion etching in a chlorine-base gas. According to this technique, the magnetic substance layer is processed into minute dimensions in a shorter time, compared to the method of processing the magnetic substance layer by ion milling.
The pole portion layer 111a, formed by etching a film to be patterned made of a high saturation flux density material such as FeN or FeCo, easily reacts with water. Corrosion is therefore likely to occur in the pole portion layer 111a during the etching step as shown in FIG. 11A and FIG. 11B and the following steps. Numeral 120 indicates a corroded portion.
If the film to be patterned is etched through reactive ion etching to form the pole portion layer 111a, molecules of a component of a reactive gas deposit on the cross-sectional surface of the pole portion layer 111a and corrosion occurs in the pole portion layer 111a. For example, if the film to be patterned is etched through reactive ion etching in a chlorine-base gas to form the pole portion layer 111a, chlorine molecules deposit on the cross-sectional surface of the pole portion layer 111a. These chlorine molecules react with water to form hydrochloric acid that corrodes the pole portion layer 111a . 
Therefore, the problem is that corrosion of the pole portion layer 111a frequently occurs if the film to be patterned made of a high saturation flux density material such as FeN or FeCo is etched through reactive ion etching, in particular. If corrosion of the pole portion layer 111a occurs, it is difficult to control the write track width, and writing characteristics such as the overwrite property and nonlinear transition shift (NLTS) are reduced.
It is a first object of the invention to provide a method of forming a patterned thin film for making the thin film having a fine pattern in a short time and for preventing corrosion of the patterned thin film.
It is a second object of the invention to provide a method of manufacturing a thin-film magnetic head for making a fine magnetic layer in a short time and for preventing corrosion of the magnetic layer.
A method of forming a patterned thin film of the invention comprises the steps of: forming a film to be patterned; forming a patterned thin film by etching a part of the film to be patterned, using reactive ion etching; and removing deposits on a cross-sectional surface of the patterned thin film that is obtained in the step of forming the patterned thin film.
According to the method of forming the patterned thin film of the invention, a part of the film to be patterned is etched through reactive ion etching to form the patterned thin film. Deposits on the cross-sectional surface of the patterned thin film are then removed.
According to the method of the invention, ion milling or reverse sputtering may be used in the step of removing the deposits.
According to the method of the invention, the film to be patterned may be etched, using a mask layer formed through plating as a mask, in the step of forming the patterned thin film. In this case, the mask layer may be made of a magnetic material capable of being formed through plating.
According to the method of the invention, the film to be patterned may be etched, using a mask layer made of an insulating material as a mask, in the step of forming the patterned thin film.
According to the method of the invention, the reactive ion etching may be performed through the use of a chlorine-base gas or a fluorine-base gas as a reactive gas in the step of forming the patterned thin film.
According to the method of the invention, the reactive ion etching may be performed at a temperature in a range of 50 to 300xc2x0 C. in the step of forming the patterned thin film.
According to the method of the invention, the film to be patterned may be formed through sputtering.
According to the method of the invention, the film to be patterned may be made of a high saturation flux density material. The high saturation flux density material of the invention is a magnetic material whose saturation flux density is 1.6 T or greater.
According to the method of the invention, the patterned thin film may be a magnetic layer that is incorporated in a thin-film magnetic head.
A method of the invention is provided for manufacturing a thin-film magnetic head including: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers; the second magnetic layer including a track width defining layer that defines a track width. The method comprises the steps of: forming the first magnetic layer; forming the gap layer on the pole portion of the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the thin-film coil such that the at least part of the coil is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The step of forming the second magnetic layer includes the steps of: forming a film to be patterned; forming the track width defining layer by etching a part of the film to be patterned, using reactive ion etching; and removing deposits on a cross-sectional surface of the track width defining layer that is obtained in the step of forming the track width defining layer.
According to the method of manufacturing the thin-film magnetic head of the invention, a part of the film to be patterned is etched through reactive ion etching to form the track width defining layer. Deposits on the cross-sectional surface of the track width defining layer are then removed.
According to the method of the invention, ion milling or reverse sputtering may be used in the step of removing the deposits.
According to the method of the invention, the film to be patterned may be etched, using a mask layer formed through plating as a mask, in the step of forming the track width defining layer. In this case, the mask layer may be made of a magnetic material capable of being formed through plating.
According to the method of the invention, the film to be patterned may be etched, using a mask layer made of an insulating material as a mask, in the step of forming the track width defining layer.
According to the method of the invention, the reactive ion etching may be performed through the use of a chlorine-base gas or a fluorine-base gas as a reactive gas in the step of forming the track width defining layer.
According to the method of the invention, the reactive ion etching may be performed at a temperature in a range of 50 to 300xc2x0 C. in the step of forming the track width defining layer.
According to the method of the invention, the film to be patterned may be formed through sputtering.
According to the method of the invention, the film to be patterned may be made of a high saturation flux density material.
The method of manufacturing the thin-film magnetic head of the invention may further comprise the step of etching a part of the first magnetic layer around the track width defining layer, using reactive ion etching, after the track width defining layer is formed.
Other and further objects, features and advantages of the invention will appear more fully from the following description.